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Avalanche Forecast

Archived

Apr 14th, 2017–Apr 15th, 2017

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

Observations from the region have been very limited recently. If you are out in the mountains, please consider posting your observations to the Mountain Information Network and help us improve the bulletin. Click here for more details.

Confidence

Low - Due to the number of field observations

Weather Forecast

SATURDAY: Cloudy with sunny periods / Light to moderate west wind / Alpine temperature -1 / Freezing level 1500mSUNDAY: Mix of sun and cloud / Light south wind / Alpine temperature 1 / Freezing level 1700mSUNDAY: Mix of sun and cloud / Light southeast wind / Alpine temperature 6 / Freezing level 2300m

Avalanche Summary

Reports on Thursday indicate numerous skier controlled and natural loose wet avalanches to size 1.5 on all aspects up to 2000m. Additionally a few explosive controlled moist storm slab avalanches were reported to size 2, 20-30cm deep on north and east aspects above 2000m. Exposure to large overhanging cornices remains a significant concern. As the sun comes out over the weekend I would expect see cornices weaken and loose snow avalanches run from steep sun exposed slopes during the warmest parts of the day.

Snowpack Summary

Up to 20cm of moist new snow fell at upper elevations Wednesday night. Thursday during the day the precipitation fell as rain up to 2000m making the snow surface moist or wet. Subsequent overnight cooling has created thin surface crusts up to 2100m. All this adds to moist new snow from the previous weekend and sits on a well developed crust layer that formed up to 1400m on all aspects except south where it formed up to 1700m. The snowpack is generally well settled and continues to transition into a spring melt/freeze regime. Below 1300m the snowpack may be moist or wet through its entire thickness. In the alpine cornices continue to grow large and ever more overhanging.

Problems

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.